Music guide
Audio Time Stretch: Changing Duration Without Changing Pitch
Estimate the new duration when you speed up or slow down audio while preserving its pitch.
Written by James — Founder & Builder, BoringToolsKit · Published 2026 · Planning information, not professional advice.
Time stretch separates speed from pitch
Normal speed change shifts both tempo and pitch together. Time stretching changes duration while keeping pitch constant, which is how DAWs can slow a vocal solo without detuning it or speed a sample up to match the grid.
The duration math
New duration equals original duration divided by the speed factor. Speeding up 2× halves the length; slowing to 0.75× lengthens it by about a third. The calculator converts any speed ratio into the resulting duration so you can plan how a stretched clip will sit in your arrangement.
Quality depends on the algorithm
Time-stretch artifacts such as warbling or smearing depend on the algorithm and the amount of stretch. Gentle changes within about 25% usually sound clean; extreme stretches can degrade transients. Knowing the target duration lets you plan how much stretching a clip actually needs.